Hydraulic motor vehicle braking system with wheel slip control

ABSTRACT

A hydraulic automotive brake system with wheel slip control, includes a pressure medium source, to which a main pressure line is connected, which leads to a wheel brake, first and second pressure relief line segments connected to the wheel brake and leading to a supply reservoir, and having a pressure modulation valve arranged in it that either separates the supply reservoir from the wheel brake or connects it to the wheel brake, as well as a control orifice valve that is arranged in the main pressure line upstream of the first pressure relief line segment, actuated by changes in the hydraulic pressure. The brake system features a pressure chamber that actuates the control orifice valve and is provided with check valves, of which one of the check valves separates the pressure chamber from a pressure medium branch of the main pressure line arranged upstream of a control orifice, the other check valve connects the pressure chamber to the connection of the pressure relief line segment to the wheel brake, and whereby a final control element is guided in a sealed manner in the first pressure chamber and is exclusively exposed to pressure from the pressure medium source in the one direction of actuation of the control orifice valve, and in the other direction of actuation is exposed to the pressure change in the pressure chamber.

BACKGROUND OF THE INVENTION

The invention relates to a hydraulic automotive brake system with wheelslip control, with a pressure medium source onto which a main pressureline is connected, which leads to a wheel brake, with a pressure reliefline that connects to the wheel brake and to a supply reservoir, and inwhich a pressure modulation valve is arranged that either separates thesupply reservoir from the wheel brake or connects it to the wheel brake,as well as with a control orifice valve arranged in the main pressureline upstream of the pressure relief line, actuated by a change in thehydraulic pressure.

A brake system of the above indicated type has become known from DE 4319 227 A1, with a pressure medium source to which a main pressure lineis connected, leading to a wheel brake. In turn, the wheel brake has aconnection for a pressure relief line which leads to a low pressurereservoir through an electromagnetically actuated outlet valve. Ahydraulic pump is connected downstream of the low pressure reservoir,leading the pressure medium of the low pressure reservoir back to themain pressure line, which is connected to a brake pressure transducer.The brake pressure transducer as well as the hydraulic pump are to beregarded as pressure medium sources to supply the wheel brakes. Anelectromagnetically actuated inlet valve is located in the main pressureline, between the connection of the auxiliary pressure pump to the mainpressure line and the connection of the outlet valve to the mainpressure line, with an orifice control valve following downstream of theinlet valve in the main pressure line. This orifice control valve ishydraulically actuated interdependent with the pressure differencebefore and after the inlet valve. The orifice control operation ishereby subject to the influence of the dynamic pressure drop inside theinlet valve. Correspondingly, to operate this orifice control valve, arelatively high switching pressure is required, the lowering of whichwould prove to be expedient.

Therefore, the object of the present invention is to fundamentallyimprove a hydraulic automotive brake system with wheel slip control ofthe generic type, such that a control orifice operation can be createdthat is simple to realize with as little medium use as possible, saidoperation, moreover, being characterized by the most simple, rapid andoperationally reliable mode of operation.

SUMMARY OF THE INVENTION

This object is achieved according to the invention by a brake systemthat features a pressure chamber and check valves, one of whichseparates the pressure chamber from a connection of the main pressureline arranged upstream of the control orifice, the other check valveconnecting the pressure chamber to the connection of the pressure reliefline to the wheel brake, that a final control element is guided in asealed manner in the pressure chamber, and in one direction of actuationof the control orifice valve this final control element is exposedexclusively to the pressure of the pressure medium source, while in theother direction of actuation it is exposed to the pressure change in thepressure chamber after the pressure modulation valve has been opened.

Further characteristics, advantages and possible applications of theinvention are explained in more detail in the following on the basis ofthree exemplified embodiments.

BRIEF DESCRIPTION OF THE DRAWINGS

In the drawings,

FIG. 1 shows a hydraulic schematic for the object according to theinvention;

FIG. 2 shows a first embodiment of the control orifice, integrated intoan electromagnetically actuated inlet valve of the brake system; and

FIG. 3 shows a further structural embodiment of the control orifice.

DETAILED DESCRIPTION OF THE DRAWINGS

The hydraulic schematic according to FIG. 1 shows the characteristicsthat are essential to the invention, according to which a main pressureline 6 is connected to a pressure medium source 10 and leads to a wheelbrake 8. With a pressure relief line 7 that is connected to the wheelbrake 8 and leads to a reservoir 19, and in which a pressure modulationvalve 20 that is closed when in the normal setting is arranged in theform of a wheel brake outlet valve. An orifice control valve 1 islocated in the main pressure line 6 upstream of the connection of thefirst pressure relief line segment 7′ to the main pressure line, saidorifice control valve according to the invention having a pressurechamber 2 allocated to it, onto which check valves 3, 4 are connected.

One of the check valves 4 has the task of separating a pressure mediumbranch 5 attached to the main pressure line 6 upstream of the controlorifice valve 1 from the pressure chamber 2. The other check valve 3connects the connection of the pressure relief line coming from thewheel brake 8 to the pressure chamber 2 Furthermore, a final controlelement 9 is located in the pressure chamber 2, guided into it in asealed manner and represented symbolically as an actuating piston. Thisfinal control element 9 is coupled to the control orifice valve 1 inFIG. 1 by means of a rod for a better overview of the operation. In theone direction of actuation of the control orifice valve 1 the piston ofthe final control element 9 is acted on exclusively by the pressure ofthe pressure medium source 10 via the pressure medium branch 5, while inthe opposite direction of actuation—after the opening of the pressuremodulation valve 20—the pressure change and thereby the drop in pressurein the pressure chamber 2 acts to switch on the orifice operation. Thefinal control element 9 and thus the control orifice valve 1 ispositioned in its non-active normal setting by means of a spring 11tensed inside the pressure chamber 2 and supported on the final controlelement 9. The control orifice valve 1 thereby also persists in thethrottle-free setting when there is a condition of no hydraulicpressure. In the hydraulic schematic the check valve 4 connected in apermanent manner to the pressure medium source 10 is inserted in aseparate line connected to the pressure chamber 2. As the furtherexemplified embodiments show, it can also be attached to the piston ofthe final control element 9. Furthermore, upstream of the controlorifice valve 1 an electromagnetically actuated inlet valve (pressuremodulation valve 17) is shown. However, in corresponding agreement withthe previously described operating elements, this is not a necessarycomponent of the brake system that is required in order to execute apressure reduction or pressure build-up phase during wheel slip control.A consequence of this is that the previously used inlet valve upstreamof the wheel brake 8 can be eliminated, since the pressure build-up andpressure reduction phases necessary for wheel slippage control arerealized by the control phases of the pressure modulation valve 20connected down-line of the pressure chamber 2. Comparatively good brakepressure control results can thus be achieved, which can besupplemented, either as desired or as required, by a precise pressuremaintenance phase through the additional use of pressure modulationvalve 17 that acts as an inlet valve. When using the pressure modulationvalve 17, the control orifice valve 1 along with the final controlelement 9 and the check valves 3, 4 form an integrated, structuralspace-optimizing unit, the construction of which is explained in thefollowing FIG. 2.

FIG. 2 shows a partial, sectioned illustration through a pressuremodulation valve 17 employed as a cartridge valve in a valve blockhousing 21. The valve push rod 16 connected to the magnet armature 22extends through a magnet core 23 into a hollow space of the valvecartridge 24, in the underside of which a shell-forming valve seat body18 is fastened. The valve seat body 18 is connected, at its lowersection, to the valve cartridge 24 that is also shell-shaped andstepped, whereby an annular space 25 remains between the valve seat body18 and the valve cartridge 24, in which space an annular collar thatforms the check valve 4 is arranged. Above the check valve 4 there is afinal control element 9 that, together with the check valve 4, forms anannular piston 12 sealed off in the annular space 25 of the valvecartridge 24. The sealing lip on the annular piston 12, as a result of abore hole 26 that extends in the annular space 25 of the valve cartridge24, is directly exposed to the pressure of the pressure medium source10, while the other check valve 3 in the form of a ring collar isarranged on the shell forming section above the annular piston 12. Thecheck valve 3 blocks the pressure chamber 2 positioned between the tworing collars in the direction of the section of the main pressure line 6that leads to the wheel brake 8. This check valve 3 is fixed to thevalve cartridge 24 by means of an annular part 13 that is attached tothe housing This check valve 3 makes the exclusively pressure mediumflow possible from the pressure medium source 10 via the valve push rod16 raised from the valve seat body 18 according to the illustration, tothe wheel brake 8 and into the pressure chamber 2. The pressure chamber2 is structurally delimited from the shell-forming final control element9 and the ring collars adjacent to the wall of the valve cartridge 24.At the same time, the pressure chamber 2 contains the spring 11, whichadjoins the shoulder of the final control element 9 with its one springend, and with the other spring end adjoins the support ring of the checkvalve 3. A bore hole passage in the valve cartridge 24 at the level ofthe pressure chamber 2 leads to pressure modulation valve 10 that isclosed when in the normal position, while in the blocked setting of saidpressure modulation valve 20 pressure medium of the pressure mediumsource 10 is under pressure between it and the pressure chamber 2. Forthe time being, in order to permit the control orifice function toremain inoperative, a hydraulic pressure force that is smaller by thespring force than the force that is exerted during normal braking by thehydraulic pressure force generated by the pressure medium source 10 issufficient in pressure space 2. The annular piston 12 that acts as anoperating piston is only displaced in the direction toward the magnetcore 23 after the pressure modulation valve 20 that is blocked in thenormal setting makes possible an escape of pressure medium from thepressure chamber 2 to the supply reservoir 19. As the shell shaped finalcontrol element 9 moves in the direction toward the magnet core 23, thepassage cross section between the shell-shaped end and the front face ofthe magnet core 23 turned toward it diminishes to the dimension of oneor more orifice openings 14, as a result of which the fluid coming fromthe pressure medium source 10 is limited in its flow rate through to thewheel brake 8. The flow rate through the control orifice can be adjustedby means of the shell gap of the final control element 9 from the magnetcore 23, as well as by the appropriate structural modification, forexample in a photo-technical way by means of etching the orificeopenings 14, and orifice channels are put into a thin, sheet metal part15 that is adjacent to the magnet core 23 In this way cost-effective,discretionary selections can be achieved by manufacturing thin, sheetmetal parts 15 with varying orifice openings 14. As an alternative tothe etching process the orifice opening 14 can, for example, be appliedas a bore or a slot in the shell shaped end of the final control element9.

The change-over pressure of the orifice valve 1 in the orifice settingis relatively small, since large annular collars can be used as a resultof the structural design of the check valves 3, 4, whereby the slightforce of the spring 11 is relatively small and is thereby to be viewedas advantageous for the change-over behavior in the orifice setting. Theresult is a compact, integrated, quasi-static control orifice valve 1 asderived from the structural embodiment as well as from FIG. 1, thecontrol orifice of which does not switch under the influence of thedynamic pressure drop through the electromagnetic inlet valve (pressuremodulation valve 17) As a result of the fact that the control orificevalve 1 at this stage can be switched into the orifice stettingindependent of the dynamic pressure drop through the electromagneticallyactuated inlet valve, the calibration measures previously common, forexample by using a series of orifices, can be eliminated. Consideringthe very small change-over pressure in the orifice setting, reliable andcomfortable operation thus results.

To the extent that the electromagnetic inlet valve (pressure modulationvalve 17) is not used for brake pressure control, a hydraulic brakesystem results that has wheel slip control with a reduced number ofsolenoid valves, which can lead to the construction of the controlorifice valve 1 as illustrated in FIG. 3.

FIG. 3 shows an expedient embodiment of the control orifice valve 1integrated into a preferably block-shaped valve block housing 21 of theslip regulated brake system. The receiving housing for the controlorifice valve 1 features a blind bore into which a main pressure line 6connected to the wheel brake 8 discharges laterally, and there is aconnection to the pressure chamber 2 by means of the check valve 3adjacent to the section of the main pressure line 6. The second pressurerelief line segment 7″ discharging laterally into the pressure chamber 2is connected to the pressure modulation valve 20. The check valve 3 isequivalent to the embodiment according to FIG. 2, designed as a ringcollar that is fastened to one shell-shaped annular part 13, which isfixed between a step of the bore and a cover 27 that covers the blindbore. Equally, the annular part 13 at its interior receives an annularfilter 28, which keeps impurities in the pressure medium coming from thewheel brake 8 from the orifice openings 14. Furthermore, at the end ofthe blind bore hole there is a plate filter 29 which also assures thatdirt particles brought from the pressure medium source 10 into the mainpressure line 6 are kept from the annular piston 12 and thereby from thecheck valves 3, 4 and the orifice openings 14. The annular piston 12 isdesigned shell-shaped over nearly its entire section, so that thisreceives the spring 11 in its interior, said spring being supported onthe front face of the cover 27 with its end that faces away from theannular piston 12, The orifice openings 14 in the present case areimbedded in a thin, sheet metal part 15 by means of an etching process,said thin sheet metal part being clamped between the annular part 13 andthe cover. Alternatively, however, it is possible that one or moreorifice openings 14 are imbedded in the end area of the shell shapedsection on the annular piston 12. From the drawing it becomes evidentthat the shell shaped section at the annular piston 12 is guided in theannular part 13. The ring collar (check valve 4) acted on immediatelyafter the plate filter 29 in the direction of closing by the pressuremedium in the main pressure line 6 is also inserted in a recess on theexpanded part of the annular piston 12, in the same manner as the checkvalve 3.

In the operational release position, which corresponds to the normalposition of the control orifice valve 1 as illustrated, the area of theannular piston 12 that receives the check valve 4 is supported on theplate filter 29. Upon actuation of the brake and thereby an executedpressure build up in the main pressure line 6, the pressure mediumextends through the hollow area of the annular piston 12 and through theannular filter 28 to the wheel brake 8, as well as through theintermediate space of the sealing lip on the check valve 3 and thehousing walls, into the pressure chamber 2. The pressure mediumdisseminates from there through the second pressure relief line segment7″ to the pressure modulation valve 20, which is closed in the normalsetting. Since the same brake pressure exists on both sides of the checkvalve 4 and the annular piston 12 is pressure-equilibrated, thispersists in the normal setting as illustrated. Upon the electromagneticopening of the pressure modulation valve 20 a pressure gradient resultsin the pressure chamber 2, whereby the annular piston 12 is no longerpressure equilibrated. This moves, as a consequence of the pressureforce generated by the pressure medium source 10 with its shell shapedsection acting on the thin, sheet metal part 15. The pressure mediumthat flows into the hollow space of the annular piston 12 through thecalibration opening 30 thus extends exclusively in the direction of themain pressure line 6 that leads to the wheel brake 8 through orificeopening 14, and thereby through the check valve 3 in the direction ofthe opened pressure modulation valve 20. As a result of the fact thatthe orifice opening cross section 14 is considerably smaller than theopening cross section of the pressure modulation valve 20, the pressuredecreases in the wheel brake 8 in the direction of the pressure-lesssupply reservoir 19, which corresponds to a low pressure reservoir in abrake system that functions according to a recirculating principle. Thebrake pressure decrease in the associated wheel brake 8 is accomplishedas a result of the change-over setting of the control orifice valve 1 asdescribed at this stage. A new build up of brake pressure in the wheelbrake 8 requires the reversal of the pressure modulation valve 20 intothe blocking position, whereby renewed filling of the pressure chamber2, along with the action of the spring 11, causes the ring piston 12 totravel back into its illustrated normal setting, A rapid release of thewheel brake 8 is accomplished by the overflow of the two check valves 3,4 in the direction of the pressure medium source 10, as soon as thepressure level in the pressure medium source 10, that is, in the mastercylinder, is lowered by means of the release of the brake pedal. Withregard to the construction illustrated according to FIG. 3, aparticularly compact unit results for the control orifice valve 1, sinceall essential, previously described individual elements that arerotationally symmetrical and coaxially interstaged are arranged in ablind bore hole. The same system characteristics also result for theembodiment according to FIG. 2.

REFERENCE LIST

1. control orifice valve

2. pressure chamber

3. check valve

4. check valve

5. pressure medium branch

6. main pressure line

7. pressure relief line

7′. first pressure relief line segment

7″. second pressure relieve line segment

8. wheel brake

9. final control element

10. pressure medium source

11. spring

12. annular piston

13. annular part

14. orifice opening

15. thin sheet metal part

16. valve push rod

17. pressure modulation valve

18. valve seat body

19. supply reservoir

20. pressure modulation valve

21. valve block housing

22. magnet armature

23. magnet core

24. valve cartridge

25. annular space

26. bore hole

27. cover

28. annular filter

29. plate filter

30. calibration opening

REFERENCE LIST

1. control orifice valve

2. pressure chamber

3. back pressure valve

4. back pressure valve

5. pressure medium branch

6. main pressure line

7. pressure medium drain line

8. wheel brake

9. final control element

10. pressure medium source

11. spring

12. annular piston

13. annular part

14. orifice opening

15. thin sheet metal part

16. valve push rod

17. pressure modulation valve

18. valve seat body

19. supply reservoir

20. pressure modulation valve

21. valve block housing

22. magnet armature

23. magnet core

24. valve cartridge

25. annular space

26. bore hole

27. cover

28. annular filter

29. plate filter

30. calibration opening

What is claimed is:
 1. A hydraulic automotive brake system with wheelslip control, comprising: a pressure medium source onto which a mainpressure line is connected, which leads to a wheel brake, a pressurerelief line including first and second pressure relief line segments,wherein said first and second relief line segments connect the wheelbrake to a supply reservoir, a pressure modulation valve coupled to saidmain pressure line that either separates the supply reservoir from thewheel brake or connects it to the wheel brake, a control orifice valvearranged in the main pressure line upstream of the pressure relief line,actuated by a change in the hydraulic pressure, a pressure chamber andfirst and second check valves, wherein said first check valve separatesthe pressure chamber from a connection of the main pressure line, andwherein the second check valve is disposed within the first segment ofthe pressure relief line, wherein said first segment of said pressurerelief line extends from said pressure chamber to said main pressureline a final control element guided in a sealed manner in the pressurechamber, wherein in a first direction of actuation of the controlorifice valve the final control element is exposed exclusively to thepressure of the pressure medium source, and a second direction ofactuation the final control element is exposed to the pressure change inthe pressure chamber after the pressure modulation valve has beenopened.
 2. A brake system according to claim 1, wherein the finalcontrol element positions the control orifice valve in its inactivenormal setting by means of a spring arranged in the pressure chamber. 3.A brake system according to claim 1, wherein the first and second checkvalves are connected in series in terms of effect relative to thepressure chamber such that the pressure medium of the wheel brake canescape through the pressure chamber to the pressure medium source.
 4. Abrake system according to claim 1, wherein the check valves arestructurally positioned on the final control element.
 5. A brake systemaccording to claim 1, wherein the check valves are designed as collarvalves.
 6. A brake system according to claim 1, wherein the finalcontrol element includes an annular piston that receives the first checkvalve that is exposed to the direct pressure of the pressure mediumsource in the area of a large, front cross section, while the secondcheck valve seals off the pressure chamber along a shell-shaped sectionof the annular piston in the direction toward the pressure mediumconnection of the wheel brake.
 7. A brake system according to claim 6,wherein the second check valve is fixed to an annular part that isattached to the housing.
 8. A brake system according to claim 6, whereinthe shell-shaped end section of the annular piston is positioned in asealed manner on a thin, sheet metal part that features at least oneorifice opening and that is anchored rigidly to the housing.
 9. A brakesystem according to claim 6, wherein the annular piston is arrangedcoaxial to a valve push rod of the pressure modulation valve that isopen when in the normal position.
 10. A brake system according to claim9, wherein the annular piston is guided in a translational direction ona shell shaped valve seat body of the pressure modulation valve, whereinthe pressure modulation valve is arranged upstream of the controlorifice valve.